The field of the invention is cermet bodies which have first phase or phases of nonoxide ceramic compound and second phase or phases of metal, alloy and/or intermetallic compound. The nonoxide ceramic compounds are boride, nitride, silicide, sulfide and combination thereof. A combination of these compounds can be either two discrete phases or a single complex phase.
Most commonly heretofore, these cermet bodies have been of the type physically formed of ingredients corresponding to the crystalline phases in the bodies. By way of exemplary illustration, reference is made to the following prior art documents. U.S. Pat. No. 3,037,857 discloses mixing, shaping and heating particulate refractory metal boride with either powdered or molten aluminum metal or alloy to yield solid cermet bodies of the same boride and metal or alloy phases. U.S. Pat. No. 3,274,093 discloses cold-pressing titanium diboride powder to form a porous body that is impregnated with molten aluminum. Belgian Pat. No. 644066, U.S. Pat. No. 3,178,807 and U.S. Pat. No. 3,459,515 disclose mixing, explosively compacting and heating particulate mixtures of aluminum and certain carbide and/or boride to yield bodies of essentially the same aluminum and carbide and/or boride phases. U.S. Pat. No. 3,328,280 discloses mixing and, either simultaneously or sequentially, pressing and heating particulate mixtures of aluminum nitride and titanium diboride and/or aluminum.
Cermet bodies of the type described in the preceding paragraph have properties which are dependent upon and limited by the inherent effects of the physical nature of their ingredients which are physically combined. The distribution and sizing of the phases are generally directly related to the particle sizing and mixing of ingredient powders and to sizing and distribution of pores in a porous body that is impregnated. The powders are not always easily available in uniformly fine sizes for obtaining superior properties. Milling of powders to improve their sizing can lead to oxidation contamination of the metal and nonoxide powders in the absence of controlled atmosphere milling requiring extra cost. In fact, some powders such as TiB.sub.2 in sizes of 5 .mu.m or finer present fire and explosion hazard during milling due to their rapid reaction with oxygen in air under conditions of frictional heating. Oxidation contamination often interferes with proper sintering of the powder mixtures, with or without simultaneous pressing, so that the resultant body is weak and has relatively poor properties. Although explosive compaction was proposed to overcome the latter difficulty, it has serious drawbacks that limit its usefulness, as is explained in the article by C. Hoening and C. Yust entitled "Explosive Compaction of AlN Amorphous Si.sub.3 N.sub.4, Boron, and Al.sub.2 O.sub.3 Ceramics" in the American Ceramic Society Bulletin, Vol. 60 (1981) beginning at p. 1175.
Amongst numerous reactions for forming other types of multiphase bodies by an unusual reaction hot pressing process involving passage of electric current through the reaction mixture during the process, U.S. Pat. No. 3,143,413 discloses only one reaction hot pressed cermet of metal and nonoxide ceramic phases, viz. the molar combination of Ni+2BN+TiN+2 ZrC, but no details are given about the properties of such body made from -60 mesh starting powders hot pressed at temperature between 1800.degree.-2300.degree. C.
There has been a continuing need for cermets of metal and nonoxide phases with easily controlled and predictable composition, crystal structure (including uniform phase distribution and fine grain size) and related physical properties, and which can be easily and economically fabricated in a variety of shapes.